The present invention relates to a plasma display panel for displaying an image by light emission of a plurality of discharge cells, a method of fabricating the same, and a display apparatus using the plasma display panel.
A display apparatus using a plasma display panel which contains a plurality of discharge cells is constructed to display an image by applying a voltage across electrodes of each discharge cell and thereby causing the desired discharge cell to emit light. A panel unit, which is the main part of the plasma display panel, is fabricated by bonding two glass base plates together in such a manner as to sandwich a plurality of discharge cells between them.
In the thus constructed plasma display panel of the prior art, the discharge cells caused to emit light for image formation generate heat, which causes the temperature of the plasma display panel to rise. The heat generated in the discharge cells is transferred to the glass forming the base plates, but because of the properties of the base plate material, the heat conduction in directions parallel to the panel face is difficult. Furthermore, the temperature of a discharge cell activated for light emission rises markedly, while the temperature of a nonactivated discharge cell does not rise much. This has presented the problem that, in the prior art plasma display panel, the panel face temperature of the plasma display panel rises locally, accelerating thermal deterioration of affected discharge cells, unless some heat sinking measures are taken.
Further, since the temperature difference between activated and nonactivated discharge cells is very large, a stress is applied to the panel unit, the resulting problem being that the panel unit of the prior art plasma display panel is prone to breakage.
When the voltage to be applied to the electrodes of discharge cells is increased, the brightness of the discharge cells increases but the amount of heat generation in such cells also increases. Discharge cells whereto large voltages are applied for activation therefore become more susceptible to thermal deterioration; and the cells tend to exacerbate the breakage problem of the panel unit of the plasma display panel.
FIG. 12 is a schematic cross-sectional view showing a heat sinking structure of a plasma display panel according to the prior art. As shown in FIG. 12, a supporting plate 300 is provided on, covering the entire back surface of a panel unit 550 of the prior art plasma display panel (hereinafter abbreviated as PDP) 500. The PDP 500 is supported by the supporting plate 300. The PDP 500 is fixed in place by means of double-sided adhesive tapes 310 attached along both edges of the supporting plate 300. In the prior art PDP 500, a heat conductive silicone sheet is interposed between the panel unit 550 and the supporting plate 300 to transfer the heat generated in the PDP 500 to the supporting plate 300. However, in the prior art PDP 500 using the silicone sheet, since the panel unit 550 is curved, it has been difficult to bring the entire panel unit 550 into intimate contact with the supporting plate 300.
In the prior art PDP 500 shown in FIG. 12, a heat conductive liquid (comprising silicone grease and alumina, and the like) 330 is filled between the panel unit 550 and the supporting plate 300 to completely fill the gap between them. In this way, in the prior art PDP 500, the gap between the panel unit 550 and the supporting plate 300 is filled with the heat conductive liquid 330 via which the opposing faces of the panel unit 550 and supporting plate 300 are contacted with each other in a heat conductible manner over the entire regions thereof.
Further, in the prior art PDP 500, fins 320 are formed over almost entire surface on the rear side of the supporting plate 300. With this structure, it is claimed that the heat generated in the panel unit 550 of the prior art PDP 500 is transferred to the supporting plate 300 via the heat conductive liquid 330 and dissipated through the fins 320.
However, even if the space formed between the panel unit 550 and the supporting plate 300 is filled with the heat conductive liquid 330, the problem of global or local temperature rise in the panel unit 550 cannot be solved for reasons explained below.
That is, the heat conductivity of the conventional heat conductive liquid 330 is poor compared with other heat sinking material such as aluminum, and moreover, the layer of the heat conductive liquid 330 has a thickness amounting to a few millimeters; as a result, the heat generated in discharge cells 400 is not sufficiently transferred to the fins 320, but is accumulated in the panel unit 550 of the PDP 500. Furthermore, when the panel unit size is increased, the layer thickness of the heat conductive liquid 330 becomes thicker, resulting in a structure tending to further increase the temperature of the panel unit 550.
In the conventional prior art PDP 500, effort has been made to reduce the space formed between the panel unit 550 and the supporting plate 300 in order to enhance the efficiency of heat transfer from the panel unit 550 to the fins 320. However, the curvature and the degree of curvature of the panel unit 550 differ for each individual panel unit, and also, the supporting plate 300 does not have a perfectly flat surface. As a result, it has been impossible to bring the opposing faces of the panel unit 550 and support plate 300 into perfect contact with each other.
In order to solve this problem, the prior art display apparatus is provided with cooling fans which impel air to promote heat dissipation through the fins. However, when such fans are mounted in the display apparatus, since the lifetime of fan bearings is shorter than that of the panel unit, it becomes necessary to replace the fan bearings during the life of the display apparatus. Furthermore, the provision of fans causes a noise problem.
In the prior art display apparatus, therefore, it has been demanded that the number of fans installed in the display apparatus be reduced, and also that an apparatus not requiring a fan (a fanless apparatus) be developed.